ListValuedMap (Apache Commons Collections 4.2 API)

Type Parameters:

K - the type of the keys in this map

V - the type of the values in this map

All Superinterfaces:

MultiValuedMap<K,V>

All Known Implementing Classes:

AbstractListValuedMap, ArrayListValuedHashMap
```
public interface ListValuedMap<K,V>
extends MultiValuedMap<K,V>
```
Defines a map that holds a list of values against each key.
A ListValuedMap is a Map with slightly different semantics:
- Putting a value into the map will add the value to a List at that key.
- Getting a value will return a List, holding all the values put to that key.
Since:

4.1

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`List<V>`	`get(K key)`	Gets the list of values associated with the specified key.
`List<V>`	`remove(Object key)`	Removes all values associated with the specified key.

Methods inherited from interface org.apache.commons.collections4.MultiValuedMap
asMap, clear, containsKey, containsMapping, containsValue, entries, isEmpty, keys, keySet, mapIterator, put, putAll, putAll, putAll, removeMapping, size, values

- Method Detail
  - get
```
List<V> get(K key)
```
    Gets the list of values associated with the specified key.
    This method will return an empty list if MultiValuedMap.containsKey(Object) returns false. Changes to the returned list will update the underlying ListValuedMap and vice-versa.
    
    Specified by:
    
    get in interface MultiValuedMap<K,V>
    
    Parameters:
    
    key - the key to retrieve
    
    Returns:
    
    the List of values, implementations should return an empty List for no mapping
    
    Throws:
    
    NullPointerException - if the key is null and null keys are invalid
  - remove
```
List<V> remove(Object key)
```
    Removes all values associated with the specified key.
    The returned list may be modifiable, but updates will not be propagated to this list-valued map. In case no mapping was stored for the specified key, an empty, unmodifiable list will be returned.
    
    Specified by:
    
    remove in interface MultiValuedMap<K,V>
    
    Parameters:
    
    key - the key to remove values from
    
    Returns:
    
    the List of values removed, implementations typically return an empty, unmodifiable List for no mapping found
    
    Throws:
    
    UnsupportedOperationException - if the map is unmodifiable
    
    NullPointerException - if the key is null and null keys are invalid